Sorry but no they are no way to downgrade the OS back to 6.1
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You would have to do this manually as Samsung does not provide a path to go back to previous versions of their UI from their latest (final release) installed versions, only from betas.
Just be careful looking into using ODIN, as while that can be done, one has to use the exact firmware for their device whether it is locked or unlocked and by region.
Thanks for the warning. I've used it before on an AT&T phone to make it stock Samsung Firmware, but I'll probably use a different phone in the meantime or attest till they add some options to make it look like ONE UI 6.1
